This is an extremely robust and effective method of welding that delivers high welding speeds and deposition rates as high as 100 pounds per hour and with no risk of incomplete fusion because of deep penetration. This method of welding is used by heavy-duty fabricators. It uses an arc between the workpiece and an electrode that is continuously fed. The powdered flux that generates a protective layer and a slag, used to add different properties to the weld pool, are used to blanket the weld zone. For the entire process, a shielding glass need not be used. The arc is engulfed in a flux and can be seen with the naked eye during the welding process.
The major advantages of using a Sub Arc Welding (SAW) process are: –
- The finish of the metal weld is of high quality.
- The process is extremely fast and the deposition rate is high.
- The finish is smooth and there is no splatter in the weld.
- Hardly any smoke is generated during the welding process.
- Protective clothing is not required because there is no arc flash used.
- The entire process is carried out using an electrode wire.
- The entire process can be easily automated for a high-operating factor.
- The process does not require any kind of manipulative skills.
This welding process is best suited for circumferential and longitudinal fillet and butt welds. Due to the fluid nature of the weld pool, lose flux layer and molten slag welding is typically carried out in a variety of positions. For joints that are circumferential, the workpiece is fixed to a head and is rotated. The welding is done in the flat position. Either a single pass, multi-pass or two-pass welds are used based on the thickness of the material. The most commonly used materials for welding are carbon-manganese steel, stainless steel, and low alloy steel.
This process is used more prominently in fabricating heavy steel plates. This also includes welding of large pipes, large structural shapes, machine components in different industries, and manufacturing huge vessels. Shipbuilders use this welding process for assembling, fabricating, and splicing many components for huge ships. Also, this welding process is used in the extensive ship repair work.
Limitations of Sub Arc Welding
Even though this process is used extensively across different industries, there are few limitations as well. One of the major limitations of this process is that the positions of the welding are very limited. The other limitations are:-
- It can be effectively used to weld only low-alloy steels.
- For this process, a high-heat input and a slow-cooling cycle are used. This can create an obstruction when welding is done on tempered and quenched steels.
- Since a heat limitation has to be adhered to during the process, high-temperature welding may not always be possible. Multiple pass welds might be used in order to get the required quality and quantity. This increases the cost and reduces the advantages related to profitability as well. When a multiple pass method has used the thickness of the weld can be significantly increased.
- In this process, the arc and the puddle during the welding process cannot be seen. This might create and ineffective weld and the overall quality of the weld is compromised.
There are different methods that can be used for Sub Arc Welding. The most frequently used method is an operator monitoring method. Here, the machine does the welding and an operator supervises it. The second most frequently used method is the automatic method. Here, the welding is done automatically with a pushbutton operation. This can be done in a semi-automatic manner as well but this method is not well known in the market.
All engineering organizations need to increase productivity and save time if they have to keep up with competition and survive. Sub Arc Welding boosts productivity by increasing the number of jobs processed on the shop floor. Innovative techniques like increased stick-out, twin-wire, and tandem welding are used to meet increased productivity goals.